Out of all the components of a garment, the one part that gets the most controversy, throughout history, has always been the hemline. The rise and fall of this line of fabric has caused more stirs and scandals than any other. But why? Mainly, it has to due with women, their perceived role in society, and how the general population perceives that role.
All throughout early history, women wore long dresses that graced the ground and covered any aspect of their legs. Under the long dresses, they typically wore long bloomers, hoops under skirt, and numerous other garments that hindered any chance of the leg to see daylight. Up until World War One, that was considered the norm, until women began to take charge of their lives, rights, and costume.
1920s: The dawn of the decade brought a new right to women, the right to vote, and with this newfound righteousness, women began to dress more comfortably. Dresses became less fitted, more fun, and shorter. Hemlines rose to an all-time low in the later twenties as the carefree, Flapper look took over.
1930s: The stock market crash of the Great Depression that swallowed most of the decade brought hemlines back down, below the knees. Women dressed more conservatively for the times, and their outfits reflected this somberness compared to the lightheartedness of the twenties.
1940s: The second World War brought rations to many things, including fabric and clothing. As women bountifully joined the workplace and, even, the war effort, for the first time, hemlines shortened with this new independence.
1950s: The end of the war, the accessibility of ready-made clothing and credit, and the idea of the "American Dream" brought a new role and glamour to fashion for women in the fifties. A decade divided by ideals and age, skirts became fuller and hemlines dropped once again to below-the-knees, as women put their focus back on the family, and they became tighter and shorter during the later years as the younger generation began to have more of a say in fashion.
1960s: The media and the youth of America began to be the strongest influences during the decade and fashion became the most varied of any decade prior due to the want to cater to the youth of America. Though starting off by mimicking the classic look of Jackie Kennedy, the miniskirt invaded in the middle, and the hippie movement closed it out in the end. Hemlines went from mid to short to long and, throughout the decade, covered everything in between, as America was torn over the military conflict in Vietnam.
1970s: Though the first decade to be mostly characterized by pants, hems still varied on skirts and dresses depending on the look. Mini, medi, and maxi skirts were worn, and, even with the strong musical influences on the decade of disco and punk, endured the era without one length being more popular than the others.
1980s to present: As history repeats itself, so does fashion, and the media and youth still have control over how the trends are received. Women's role in society is becoming stronger every day, and their influence in fashion has never wavered, though the length of the hem has.
Garment Sources
One thing that we should be thankful for in this modern age is manufactured fibers. Though polyester ruled the day in the 70s and just ended up making everyone sweaty and uncomfortable, it really paved the way for experimentation. I can't tell you how many times I've gone to list an item from the 70s and looked at the garment tag and thought, "Whaaaat??!!" at the name of the fibers written.
However, when you look at the alternatives, cotton and linen that wrinkle easily, silk that's very delicate, and wool that's itchy and gets eaten by moths, poly-blend items really make living easier. 
